To become a critical thinker, learn not to accept “truthy statements”.
If someone tells you something, even if that person appears to be a person in authority, ask them where they got the information from.
If a newspaper article says “this study indicates that…” then the next question is “who conducted the study, and how was it run? It is not enough to just accept that a study was conducted.
Not all studies have large sample sizes and control for potential influences that could impact accuracy.
Understanding political debates and news issues in a way that is deeper than simply “listening to both sides when making a decision”.